In recent years, a secondary battery, which can be charged and discharged, has been widely used as an energy source for wireless mobile devices. In addition, the secondary battery has attracted considerable attention as a power source for devices which require high output and large capacity, such as electric vehicles (EV), hybrid electric vehicles (HEV), and plug-in hybrid electric vehicles (Plug-in HEV), which have been developed to solve problems, such as air pollution, caused by existing gasoline and diesel vehicles that use fossil fuels.
Small-sized mobile devices use one or a few battery cells for each device. On the other hand, middle or large-sized devices, such as vehicles, use a battery module having a plurality of battery cells electrically connected to each other because high output and large capacity are necessary for the middle or large-sized devices.
Preferably, a battery module is manufactured so as to have as small a size and weight as possible. For this reason, a prismatic battery or a pouch-shaped battery, which can be stacked with high integration and has a small weight to capacity ratio, is usually used as a battery cell of a middle or large-sized battery module. In particular, much interest is currently focused on the pouch-shaped battery, which uses an aluminum laminate sheet as a sheathing member, because the pouch-shaped battery is lightweight and the manufacturing cost of the pouch-shaped battery is low.
In addition, the battery module is configured to have a structure in which a plurality of battery cells is combined. In the case in which overvoltage is applied to some of the battery cells, overcurrent flows in some of the battery cells, or some of the battery cells overheat, therefore, the safety and operational efficiency of the battery module are seriously concerned. For this reason, it is necessary to provide means to detect and control such overvoltage, overcurrent, or overheating. Consequently, voltage sensors are connected to the respective battery cells in order to check and control the operational state of the battery cells in real time or at predetermined time intervals. However, the installation or connection of such detection means greatly complicates the process of assembling the battery module. In addition, there is a possibility that a short circuit may occur due to a plurality of wires for the detection means. In addition, as a secondary battery is used as a power source for vehicles as the result of extension in an application range of the secondary battery, it is necessary to provide fastening members that are capable of maintaining the stable contact state of the detection means even when strong impact or vibration is applied to the secondary battery.
Generally, the voltage sensors are connected to electrode terminals of the battery cells by welding. Alternatively, the voltage sensors may be physically connected to the electrode terminals of the battery cells. Specifically, the voltage sensors may be connected to the electrode terminals of the battery cells in the state in which the voltage sensors are in tight contact with the electrode terminals of the battery cells.
In the case in which the voltage sensors are connected to the electrode terminals of the battery cells by welding, however, the electrode terminals of the battery cells may be damaged. In addition, a space for welding and accuracy in welding are required. As a result, the manufacturing process is complicated, and the manufacturing cost is increased.
In the case in which the voltage sensors are connected to the electrode terminals of the battery cells in the state in which the voltage sensors are in tight contact with the electrode terminals of the battery cells, on the other hand, various kinds of problems occur. That is, when the electrode terminals of the battery cells are pressed in order to maintain the connection between the voltage sensors and the electrode terminals of the battery cells or when the electrode terminals of the battery cells are inserted into the voltage sensors, the electrode terminals of the battery cells may be damaged.
Meanwhile, in the case in which a plurality of battery cells is used to constitute a battery module or in the case in which a plurality of unit modules, each of which includes a predetermined number of battery cells, is used to constitute a battery module, a plurality of members is generally needed for mechanical fastening and electrical connection therebetween, and the process of assembling these members is very complicated. Furthermore, a space for performing the coupling, welding, or soldering of these members for mechanical fastening and electrical connection is required, with the result that the overall size of the system is increased, which is not desirable, as previously described. Therefore, there is a high necessity for a battery module that is compact and exhibits excellent structural safety.